Here's a look at the hotel's construction, which happened in just seven months.

An early architectural rendering of the proposed River Walk hotel from March 1966. Construction would begin more than a year later.

San Antonio Express-News file photo

Workers build the foundation of the Hilton Palacio del Rio Hotel on Aug. 26, 1967. Since the hotel was built next to the San Antonio River, it couldn't have a basement. Instead, foundation piers three feet in diameter and 40 feet deep were drilled and a retaining wall was built to anchor the hotel.

San Antonio Express-News file photo

H.B. Zachry and Barron Hilton oversee construction at the Hilton Palacio del Rio Hotel in August 1967. The hotel was entirely constructed without a permit, and Zachry filed for one after it was finished.

San Antonio Express-News file photo

The stretch of the San Antonio River behind the Hilton Palacio del Rio Hotel is seen during the hotel's construction in 1967.

San Antonio Express-News file photo

Construction begins on the shaft of the Hilton Palacio del Rio Hotel on Sept. 12, 1967. The shaft, which was built at an average of more than a foot per hour, houses seven guest and service elevators. Three work shifts with as many as 400 men worked around the clock to complete the shaft in time to add the guest rooms in November.